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Volume 32 (2015)
- Issue 4 Pages 411-
- Issue 3 Pages 207-
- Issue 2 Pages 95-
- Issue 1 Pages 1-
Volume 32, Issue 4
Displaying 1-9 of 9 articles from this issue
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Original Papers
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Seiji OKAWA, Keisuke ENDO, Tsutomu HOZUMI2015 Volume 32 Issue 4 Pages 411-418
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
JOURNAL FREE ACCESSCold reserving material is commonly used in the area of food transportation to preserve its low temperature and its freshness. A solvent is mainly water or salt solution. By adding around 2wt% of gel into the solvent, separation of the solvent and dispersion of the solvent in a moment of breaking the container can be prevented. However, mixing of gel suppresses the speed of solidification. Hence in this report, various types of sodium Carboxy Methyl Cellulose (CMC) were selected as cold reserving material, and influence of various parameters such as concentration, kinematic viscosity, degree of polymerization, degree of etherification on the speed of solidification were investigated. As a result, it was found with the based on the same concentration that the lower degree of polymerization gives higher speed of solidification. This is because size of the CMC molecules differs by the degree of polymerization, and the ability to eliminate CMC by freeze concentration changes. Based on the same kinematic viscosity, it was found that higher degree of etherification give higher speed of solidification, especially at low concentration. This is because of a hydrophilic phenomenon, and crystal can grow easily along CMC molecules.View full abstractDownload PDF (799K) -
Ryosuke MATSUMOTO, Tomoya YOSHIMURA, Hisashi UMEKAWA, Takeyuki AMI, Da ...2015 Volume 32 Issue 4 Pages 419-426
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
Advance online publication: October 31, 2015JOURNAL FREE ACCESSThe frost layer with melting water was measured by using a neutron radiography in the defrosting process on the aluminum finned-tube heat exchanger under the forced-convection. The water deposition distributions were estimated quantitatively in every 5 seconds for 10 minutes of the defrosting period. The melting water behavior was investigated by comparing the water deposition distribution before defrosting. The initial stage of the defrosting was referred to as the melting progressing period, in which the melting water penetrated into the water permeation layer in the frost thickness direction. The melting water penetration into the spanwise direction of the fins was not observed by the neutron radiography. After 180sec from starting the defrosting process, the frost at the fin front edge and the surrounding the tubes were melted, then, the water permeation layer was saturated by the melting water. The neutron radiography images indicated the melting water penetration into the spanwise direction of the fins. The total migration volume of the melting water into the spanwise direction was about 30% of the total frost deposition.View full abstractDownload PDF (5907K) -
Takehiro ESAKI, Noriyuki KOBAYASHI2015 Volume 32 Issue 4 Pages 427-433
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
Advance online publication: November 30, 2015JOURNAL FREE ACCESSIt is discussed system characteristics of double-stage adsorption heat pump with different adsorbent in this paper. We choose FAM-Z05 as 1st adsorbent, AC as 2nd adsorbent. This system can be operated by heat source of temperature 45-50 ℃ and generated cooling power at 15 ℃. We experimentally study the effect of double-stage system on volumetric cooling power (VCP) and Coefficient of performance (COP) in some heat source of temperature conditions. Results show that double-stage system would produce higher VCP than single-stage system at heat source of temperature 50 ℃. The value of COP on double-stage at 50 ℃ is lower than single-stage since twice amount of heat is utilized for desorption heat to FAM-Z05 and AC. Altho ugh the double-stage0 system with FAM-Z05 and AC are equal to VCP between 45 ℃ and 50 ℃, the value of COP at 45 ℃ is higher than 50 ℃. The value of COP in this double-stage system is affected by amount of sensible heat in FAM-Z05 and AC adsorber.View full abstractDownload PDF (801K) -
Yu UCHIUMI, Toru SUZUKI2015 Volume 32 Issue 4 Pages 435-440
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
Advance online publication: November 30, 2015JOURNAL FREE ACCESSEating pickled roes of various fishes is a popular custom in Japan. Tarako is a salted or salt-seasoned product prepared from walleye pollock and/or cod ovary, and accounts for the majority of pickled roe products in the Japanese market. These products are prepared using 90% or more frozen ovaries as the raw material. Freezing damage, however, is a serious issue in tarako production. To prevent freezing damage of roes, cryoprotectants such as sugars are added before freezing. Further, it has recently been demonstrated that dehydrofreezing effectively prevents freezing damage in many foods. In this study, the use of high concentrations of NaCl solution in the dehydrofreezing process during tarako production was assessed. Walleye pollock ovaries were dehydrated using 3%, 10%, 17% and saturated NaCl solution before freezing and storage. The ovaries were evaluated after thawing by drip loss, alteration in color and microscopic observation. The results revealed that the freezing damage decreased with increase in the concentration of NaCl solution.View full abstractDownload PDF (584K) -
Tomoaki KYODEN, Yukio TADA, Yuya IDA2015 Volume 32 Issue 4 Pages 441-451
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
JOURNAL FREE ACCESSThe thermoacoustic cooler is one of promising technique for utilization of unused thermal energy. The object of this paper is to study the improvement of performance in a single-loop type thermoacoustic cooler by designing of the new structure consisted of looped tube, bypass-looped tube, and two stacks as the double-loop type thermoacoustic cooler. Using finite difference time-domain (FDTD), pressure, particle velocity and phase difference were numerically simulated. Experiments were also performed to measure the cooling performance of the thermoacoustic cooler under constant electric power supplying to a speaker. Firstly, it was found that, by connecting the bypass-looped tube, the sound field was changed. As the results, the resonance frequency decreased, and the profile of velocity amplitude was shifted in the looped tube. Secondary, thermoacoustic cooling was realized in both of stacks in each looped tube due to thermoacoustic heat pumping effect. The total cooling performance of the proposed the double-loop type thermoacoustic cooler was improved in comparison with the single-loop type thermoacoustic cooler.View full abstractDownload PDF (1673K) -
Takao KOSHIMIZU , Tetsushi BIWA2015 Volume 32 Issue 4 Pages 453-459
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
Advance online publication: November 30, 2015JOURNAL FREE ACCESSThermoacoustic theory has been widely used for design of thermoacoustic devices and understanding phenomena in the devices. However, performance in a heat exchanger for thermoacoustic devices has not yet been fully understood because thermoacoustic theory cannot be applied to the heat exchanger absorbing or radiating heat. In this study, numerical analysis without thermoacoustic theory has been performed to evaluate the performance of the heat exchanger for heat absorption or heat radiation. In this paper, the influence of operating frequency on performance of the heat exchanger is investigated by introducing a heat transfer coefficient as an index for evaluating the performance. It was found that the heat transfer coefficient indicates a bigger value with increase in operating frequency and this means that the performance of the heat exchanger is improved with higher operating frequency. It is also found that heat transfer to the wall is enhanced with increase in operating frequency because the range in the radial direction affecting the heat exchange becomes smaller with higher operating frequency and thereby a temperature gradient becomes larger.View full abstractDownload PDF (536K) -
Kohei MATSUMOTO , Yoshisane NAKAMURA , Kenichi P. KOBAYASHI2015 Volume 32 Issue 4 Pages 461-468
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
JOURNAL FREE ACCESSThermoacoustic phenomenon is interconversion between the acoustic energy and the thermal energy. Thermoacoustic devices are external-combustion system and have a flexibility for choosing a heat source. They consist of a prime mover for generating sound and a heat pump for sound to compress and relax the gas within it. To generate sound waves at the prime mover, a certain temperature difference across the stack is needed. The conventional methods for heating a hot-end of stack are by placing heat exchanger at the side of stack. There are inefficiencies such as friction and heat losses at heat exchanger. In this study, to minimize friction and heat losses, radiation heat transfer is focused as the optimum heating method for the thermoacoustic prime mover. The thermoacoustic prime mover using a quartz glass tube was developed. The sunlight collected by the parabolic reflector was directly focused on the hot-end of stack. Considering the balance between sunlight to heat conversion and flow resistance, various stacks that are different from materials and channel shapes were evaluated with temperature difference and the pressure of the generated acoustic wave. For the radiation heating, the stack with low flow resistance and high specific surface area is suitable for sunlight.View full abstractDownload PDF (1485K) -
Mariko SENGA, Ryuju KASE, Shinya HASEGAWA2015 Volume 32 Issue 4 Pages 469-475
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
Advance online publication: November 30, 2015JOURNAL FREE ACCESSThe relationship between the thermal efficiency and specific acoustic impedance z in a regenerator was calculated by Ceperley in 1985. His calculation results showed that regenerator thermal efficiency is limited to around 10% of the Carnot efficiency when z of the regenerator is equivalent to the characteristic acoustic impedance of a traveling wave in free space. Furthermore, he also showed that if z can become 10 times of the characteristic acoustic impedance of a traveling wave, the thermal efficiency reaches 79% of the Carnot efficiency. In order to achieve high acoustic impedance, he explained the crosssectional area of the enlarged tube should be larger than that of the upstream duct. On the other hand, losses caused by sudden expansions in regenerator was found. These kinds of losses could be reduced by installing tapered tubes between regenerator and upstream/downstream ducts. In this study, we changed the angle of the tapered tube and measured thermal efficiency and acoustic power gain at regenerator positions of a traveling wave thermoacoustic engine. From the results, maximum thermal efficiency achieved 50.6 % of Carnot efficiency when taper angle was 7 degree.View full abstractDownload PDF (1207K) -
Shota OTAKE , Hiroaki HYODO , Testushi BIWA2015 Volume 32 Issue 4 Pages 477-483
Published: December 31, 2015
Released on J-STAGE: December 31, 2016
Advance online publication: November 30, 2015JOURNAL FREE ACCESSOne can realize an acoustic heat engine, a heat engine with no or less moving parts, as an application of thermoacoustic spontaneous oscillations of a gas column. The acoustic heat engine has been so far based on natural mode of oscillation of the gas column confined in a tube. In this study, we aim at constructing an acoustic engine with a voice coil type alternator. The alternator part is considered to replace a branch resonator of the acoustic engine made of a looped tube and the branch resonator, and thereby achieves both the lower operating frequency and the shorter engine length. This paper reports the operating condition and the performance of the combined system consisting of the engine part and the alternator part.View full abstractDownload PDF (1433K)
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